Electric circuit interrupter



De c. 25, 1945.

T. w. wlLcox ELECTRIC CIRCUIT INTERRUPIER Filed Aug. 9, 1943 Inv'entov:Thomas W. Wilcox b W ZJwJ v f His Attorneg.-

a Q P Patented Dec. 25, 1945 ELECTRIC CIRCUIT INTER'RUPTER Thomas W.Wilcox, Harrow, England, assignor to General Electric Company, acorporation of New York Application August 9, 1943, Serial No. 497,914In Great Britain August 11, 1942 4 Claims.

My invention rel-ates to electric circuit interrupters and moreparticularly to a new improved contact arrangement for electric circuitbreakers employed for the interruption of heavy currents.

It is well known that the arc energ in a circuit breaker for exampleincreases with increase in the length of the arc. Such increase in areenergy requires the dissipation of a considerable amount of heat duringthe are interrupting operation. It is desirable in circuit breakers forinterrupting heavy fault currents to keep the are drawn as short aspossible in order to maintain the arc energy at a minimum value. It isalso desirable to move the roots of the are on the associated contact soas to reduce the vaporization and consequent erosion of such contact.Many arrangements have been suggested for causing movement of the arcroots, most of which, nowever, have been fairl complicated andexpensive.

It is an object of my invention to provide new and improved means forcausing movement of the arc roots on an associated contact so as toreduce the vaporization and consequent erosion of the contact.

It is another object of my invention to provide a new and improvedarrangement in an electric circuit interrupter for maintaining the arcenergy ata minimum value.

Further objects and advantages of my invention wil1 become apparent asthe following description proceeds and the features of novelty whichcharacterize my invention will be pointed out with particularity in theclaims annexed to and forming a part of this specification.

For a better understanding of my invention reference may be had to theaccompanying drawing in which Fig. 1 is a sectional view of a portion ofan electric circuit interrupter embodying my invention, and Fig, 2 is aview taken .on line 2--.2 of Fig. 1.

Although my invention is of general application and may be used incircuit interrupters of various types, it is of particular use inalternat mg current fluid blast electric circuit breakers wherein arcextinction is brought about by the action of a blast of fluid such ascompressed air or' gas. The invention is furthermore particularlyadapted for use in fluid blast circuit breakers in which the directionof the blast is parallel with but opposite to the direction of movementof the switching member.

Referring now to the drawing, I have illustrated a cylindricalinsulating arc extinguishing chamber l0 formed of insulating materialand provided with a portion of restricted cross-sectional area H whichwill hereinafter be referred to as a nozzle, or restriction H. Mountedwithin arc extinguishing chamber ID are a pair of relatively movablecontacts comprising a fixed contact generally indicated at l2, and amovable rod contact l3. Fixed contact I2 is suitably supported abovenozzle H and is in the form of an annulus or socket member which forms anozzle contact through which the blast of fluid, such as air, isdirected. Preferably fixed contact 12 is provided with spring biasedcontact members M for electrically engaging rod contact I 3 which lattermay be in the form of a tube as shown in Fig. 1, if desired.

Any suitable means for causing relative separation between contacts I2and I3 may be provided. I have chosen to illustrate this means ascomprising a piston l5 reciprocatingly mounted in a suitable cylinderwithin arc extinguishing chamber l0. Piston I5 is operatingly connectedto rod contact I3. A suitable spring I6 is provided which biases rodcontact l3 into conducting engagement with fixed contact [2. The upwardmovement of rod contact I3 is limited by means of a stop I! supportedwithin chamber l0. Arc extinguishing chamber [0 is connected at a pointabove piston l5 and below nozzle II with a source of fluid underpressure (not shown) by means of conduit 18. In Fig. 1 the circuitinterrupter is disclosed at an intermediate point during the openingoperation when fluid under pressure is being supplied through conduit i8 causing piston 15 to move downwardly and furthermore causing a blastof fluid to flow through nozzle I l and nozzle contact [2 to extinguishthe arc drawn between relatively movable contacts l2 and I3. As soon asthe fluid under pressure supplied to conduit I8 is shut off spring IEwill force rod contact [3 toward nozzle contact l2 to reclose thecircuit. Contacts l2 and 13 are respectively connected to line terminals[9 and 20, schematically shown.

As has been pointed out above, it is essential insofar as eflicientoperation of the circuit breaker is concerned, that the arc be short andbe prevented from looping or bowing in order to keep the are energy at aminimum. When the fixed nozzle contact 12 is small in diameter itfrequently happens that in itself it suffices to prevent such bowing orlooping, but when circuit breakers are constructed for heavy currentssuch as the circuit breaker in Fig, 1, the diameter of nozzle contact l2may become so large that the arc can form a considerable loop beyondnozzle contact l2. My invention is particularly concerned bersdefinitely prevents bowing orlooping and' also minimizes erosion of thecontact because the.

are roots cannot remain at any one fixed point on the contact.

Accordingly, in the drawing I have provided a plurality of arcingmembers 2! associated with fixed contact [2 as will become apparent fromthe 'following description which are arranged with their longitudinalaXes in a plane at right angles to the path of movement of movablecontact is and disposed tangentially to a circle concentric with theaxis of'this path 'of movement. I have illustrated arcing contacts 2| asbeing welded or otherwise suitably fastened to an annular conductingmember 22 which is suitably mounted above contact l2. and electricallyconnected thereto. In this way, the arcing members 2! are arranged to beconnected to one another at their outer ends and also to the source ofcurrent supply through terminal IS. The arcing members, furthermore, allextend in the same direction from the circle to which they aretangential, which may be clockwise or counterclockwise. In Fig. 2, Ihave illustrated the arcing members as extending from the circle towhich they are tangential in a counterclockwise direction.

When fluid under pressure is supplied to arcing chamber I!) throughconduit I3 an arc is drawn between relatively separable contacts 12 andI3 and a blast of fluid through nozzle ii and nozzle contact I2 tendsrapidly to cool the arc and cause extinguishment thereof. The fluidblast will cause the arc to extend upwardly so that the arc roots strikeon one of the arcing members 25. will be observed, therefore, that whenthis happens a current loop is present and the electromagnetic force byvirtue of the current flowing in this loop will tend to bow the loop sothat the arc will move toward the inner tip 2| of the arcing member 2|,from which it will move to the next adjacent arcing member whereupon theprocess will be repeated so that the arc will be transferred from arcingmember to arcing member in a substantially circular path in a clockwisedirection, as viewed in Fig. 2. Although in the drawing I haveillustrated four arcing members arranged substantially at right angleswith each other, it will be obvious that more or less arcing members maybe provided.

In view of the detailed description included above, the operation of thecircuit interrupting device embodying my invention will be obvious. Withthis arrangement a very simple means for causing movement of the arcroots to prevent erosion of the contacts is obtained and furthermore thearc is prevented from bowing or becoming unduly long by arcing members2! thereby maintaining the arcing energy at a minimum.

While I have described a particular embodiment of my invention, it willbe obvious to those skilled in the art that various changes andmodifications may be made without departing from my invention, and I,therefore, aim in the appended claims to cover all such changes andmodifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent in the UnitedStates is:

1. In an electric circuit breaker, a pair of relatively movable contactscomprising a fixed contact and a movable contact, means for producingrelative separation of said contacts to draw'an arc therebetween, aconducting member electrically connected to said fixed contact andnormally carrying no current, a plurality of arcing members arrangedwith their longitudinal axes in a plane at right angles to the path ofsaid movable contact and being mechanically supported and electricallyconnected to said conducting member, said arcing members being disposedtangentially to a circle concentric with the axis of said path of saidmovable movable contact, and means fortransferring said are from saidfixed contact to one of said arcing members, the arrangement of saidarcing members with respect to each other and the contacts being suchthat the path of the current flowing between said movable contact andsaid conducting member including said are is in the form of a loop sothat the electromagnetic force produced causes the arc roots to movefrom arcing member to arcing member thereby minimizing erosion of saidmembers.

2. In an electric circuit breaker, a pair of relatively movable contactscomprising a fixed contact and a movable contact, means for producingrelative separation of said contacts to draw an arc therebetween, anannular conducting member electrically connected to said fixed contactand normally carrying no current, a plurality of arcing members arrangedwith their longitudinal axes in a plane at right angles to the path ofsaid movable contact and being mechanically supported and electricallyconnected to said annular member, said arcing members being disposedtangentially to a circle concentric with the axis of said path of saidmovable contact, and means for transferring said are from said fixedcontact to one of said arcing members, the arrangement of said arcingmembers with respect to each other and the contacts being such that thepath of the current flowing between said movable contact and saidannular member including said are is in the form of a loop so that theelectromagnetic force produced causes the arc roots to move in agenerally circular path from arcing member to arcing member therebyminimizing erosion of said mem bers.

3. In an electric circuit interrupter for controlling an associatedelectric circuit comprising'a pair of contacts at least one of which ismovable so that said contacts are separable to draw an arc therebetween,means for connecting said contacts with said associated circuit, one ofsaid contacts having associated therewith, in conducting relation, aplurality of fixed arcing members arranged with their longitudinal axisat an angle approximating a plane normal to the path of the movingcontact, each arcing member being disposed tangentially to a circlesurroundingthe axis of said path with all of said arcing membersextending in the same. direction from the circle to Which they aretangential, o that an are drawn between said contacts will engage saidarcing members sequentially being moved from one to another by theelectromagnetic force of the current in the are, thereby to minimizeerosion of the members and accordingly. to minimize the amount ofmetallic vapor in the arc and therefore facilitate the inter!- ruptionof the arc.

4. In an electric circuit interrupter comprising a pair of contacts atleast one of which is movable so that said contacts are separable todraw an arc therebetween, an arcing member normally carrying no currentarranged with its longitudinal axis in a plane at right angles to thepath of said movable contact and disposed tangentially to a circleconcentric with the axis of said path, and means for causing the arcdrawn between said contacts to appear between said movable contact andsaid arcing member whereby the path of the current flowing through saidarc is in the form of a loop so that the electromagnetic force producedcauses the arc to move along said arcing member to minimize erosion ofsaid member.

THOMAS W. WILCOX.

